Green house gases, global warming- cases, effects and control measures

Greenhouse gases

A greenhouse gas (GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone. Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would be on average about 33 °C (59 °F) colder than at present.

However, since the beginning of the Industrial Revolution, the burning of fossil fuels has contributed to the increase in carbon dioxide in the atmosphere from 280 ppm to 390 ppm, despite the uptake of a large portion of the emissions through various natural "sinks" involved in the carbon cycle. Anthropogenic carbon dioxide (CO₂ ) emissions come from combustion of carbonaceous fuels, principally wood, coal, oil, and natural gas.

Atmospheric concentrations of greenhouse gases are determined by the balance between sources (emissions) and sinks (the removal). 

Gas	Formula	Contribution (%)
Water vapor	H2O	36 – 72 %
Carbon dioxide	CO2	9 – 26 %
Methane	CH4	4 – 9 %
Ozone	O3	3 – 7 %

Causes

The main cause of global warming is emission of  greenhouse gases due to human activity are:

§  burning of fossil fuels and deforestation leading to higher carbon dioxide concentrations in the air. Land use change (mainly deforestation in the tropics) account for up to one third of total anthropogenic CO₂emissions.

§  livestock enteric fermentation and manure management, paddy rice farming, land use and wetland changes, pipeline losses, and covered vented landfill emissions leading to higher methane atmospheric concentrations. Many of the newer style fully vented septic systems that enhance and target the fermentation process also are sources of atmospheric methane.

§  use of chlorofluorocarbons (CFCs) in refrigeration systems, and use of CFCs and halons in fire suppression systems and manufacturing processes.

§  agricultural activities, including the use of fertilizers, that lead to higher nitrous oxide (N₂O) concentrations.

 

Effects

·         Rising sea levels and observed decreases in snow and ice extent are consistent with warming. 

·         Most ecosystems will be affected by higher atmospheric CO₂ levels, combined with higher global temperatures. Overall, it is expected that climate change will result in the extinction of many species and reduced diversity of ecosystems.

·         Vulnerability of human societies to climate change mainly lies in the effects of extreme-weather events rather than gradual climate change. Impacts of climate change so far include adverse effects on small islands, adverse effects on indigenous populations in high-latitude areas, and small but discernable effects on human health. 

·         Over the 21st century, climate change is likely to adversely affect hundreds of millions of people through increased coastal flooding, reductions in water supplies, increased malnutrition and increased health impacts.

·         Future warming of around 3 °C (by 2100, relative to 1990–2000) could result in increased crop yields in mid- and high-latitude areas, but in low-latitude areas, yields could decline, increasing the risk of malnutrition. A similar regional pattern of net benefits and costs could occur for economic (market-sector) effects. Warming above 3 °C could result in crop yields falling in temperate regions, leading to a reduction in global food production. Most economic studies suggest losses of world gross domestic product (GDP) for this magnitude of warming.

Control          

·         Use cleaner, less polluting, technologies. Use of these technologies aids mitigation and could result in substantial reductions in CO₂ emissions.

·         Policies include targets for emissions reductions, increased use of renewable energy, and increased energy efficiency.

·         Carbon capture and storage, a process that traps CO₂ produced by factories and gas or coal power stations and then stores it, usually underground.

·         Geoengineering technologies like Ocean fertilization, Capturing and sequestering CO_2, Techniques (biochar), composting